Genetic, immunologic and virologic characteristics of systemic lupus erythematosus (SLE) will be analyzed in a closed colony of dogs. A protein isolated from kidneys of canine SLE cross-reacts immunologically with retrovirus p30. Antisera to this protein are in preparation and will be used to characterize further its relationship to p30, as well as the disease. Lymphocytoxic antibodies in canine SLE will be analyzed with regard to functional properties and specificities for subsets of lymphocytes. Analyses of lymphocyte function in canine SLE are in progress.